this a oddly satisfying genre instead of usual heroes fighting the Demon lord army, evil beings are fighting them instead.
Well, while a lot of the characters themselves may have evil tendencies and potential, it seems it's more treated like an alignment without strict rules as to how they're supposed to interact with other people, and so on. The MC, while looking like a demon god to others, retains his own personality, although he does have the capabilities of being ruthless to those who attack his people. But honestly, that isn't limited to just evil factions, literally anyone from any faction could choose to show cold ruthlessness to enemies. It's just that our MC has more vile ways of dealing with his enemies. But at the end of the day, this only seems to be mostly true with MC and his faction of evil. Can't say the same for others of the evil faction within this world as it seems to be a system mixed with the game that MC played, and an RPG.